Polydiacetylene (PDA) Liposome-Based Immunosensor for the Detection of Exosomes

Exosomes are extracellular vesicles (EVs) that have attracted attention because of their important biological roles in intercellular communication and transportation of various biomolecules, including proteins and genetic materials. However, due to difficulties in their selective capture and detection, further application of exosomes remains challenging. To detect EVs, we fabricated a liposomal biosensor based on polydiacetylene (PDA), a conjugate polymer that has been widely used in sensing applications derived from its unique optical properties. To confer selectivity and sensitivity to the sensory material, antibodies targeting CD63, a membrane protein exclusively found in exosomes, were attached to the PDA liposomes and phospholipid molecules were incorporated into the PDA vesicles. Signal analysis derived from PDA liposomes for exosome detection and quantification was performed by observing colorimetric changes triggered by the ligand–receptor interaction of PDA vesicles. Visual, UV–visible, and fluorescence spectroscopic methods were used to obtain signals from the PDA lipid immunosensor, which achieved a detection limit of 3 × 10⁸ vesicles/mL, the minimum concentration that can be used in practical applications. The strategies used in the system have the potential to expand into the field of dealing with exosomes.